Update pytest-cov requirement from ~3 to ~4

Updates the requirements on [pytest-cov](https://github.com/pytest-dev/pytest-cov) to permit the latest version.
- [Changelog](https://github.com/pytest-dev/pytest-cov/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-cov@v3.0.0...v4.1.0)

---
updated-dependencies:
- dependency-name: pytest-cov
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

pyproject.toml

@@ -45,7 +45,7 @@ isort = "~5"
 mkdocs-material = "~8"
 mypy = "~1"
 pytest = "~7"
-pytest-cov = "~3"
+pytest-cov = "~4"
 types-setuptools = "^57.4.17"
 types-requests = "^2.27.30"